One of the long-term goals in electronics technology has been to provide higher functionality at a lower cost, and in a more compact package. Electronic data modules are no different. There is a constant struggle to increase memory capacity and access speed, while at the same time decreasing module cost and size. The numerous innovations disclosed herein are believed to contribute to a major advance in this direction.
As a result of the aforementioned trend toward compactness, data modules have been constructed using integrated circuit technology, and using very small casings which provide contacts whereby such data modules may be accessed. Current modules, however, have not met commercial expectations, particularly in the areas of reliability and module life. Data often is lost or miscommunicated due to dead batteries, or to poor electrical connections within the module itself. The data module disclosed in U.S. Pat. No. 4,982,371 to Bolan et al., for example, has many limiting features, including limitations related to the use of onboard battery power, and to the abundance of electrical connections between module components. The Bolan module is shown in FIG. 10 of the drawings.
The Bolan module, it will be noted, contains six distinct components, all of which must be electrically connected to make the module work. These components are: 1) a first casing half, 2) a second casing half, 3) a battery, 4) an integrated circuit, 5) a flexible circuit board, and 6) an elastic conductive material. The Bolan module thus has many connections, each connection making the module less reliable, or more likely to fail. The connections are: 1) the first casing half to the elastic conductive material, 2) the elastic conductive material to the printed circuit board, 3) the printed circuit to the integrated circuit, 4) the printed circuit board to the positive battery terminal, and 5) the negative battery terminal to the second casing half.
The Bolan module also employs an onboard battery, the module life thus extending only as long as the battery life. Once the battery voltage deteriorates to a point that the memory loses data, the module is no longer useful. Because all batteries self discharge, it will be understood that failure of the module and a loss of the data contained therein will eventually result. Additionally, the rate of battery discharge may be accelerated by various factors, including the number of transactions that the module performs, the temperature, and the RAM memory size. Further, because batteries generally include hazardous materials such as lithium and mercury, the Bolan data module may be environmentally unsafe.
The casing of the Bolan module also is unsuitable, it being difficult to mount or attach the module to physical items. The Bolan module's casing, it will be noted, is divided into first and second casing halves. This two-part casing makes it difficult to "pot" internal components, a procedure often used to ensure that all electrical connections are secure. The Bolan module instead relies on an elastic conductive material which applies pressure to contact points on the first and second casing halves. Potting material must be kept clear of these contact points. This is accomplished by pouring potting material into one-half of the casing, and then fitting the other half of the casing over the first casing half. If too much potting material is poured into the first casing half, an open contact can result. If too little potting material is poured into the first casing half, the casing can be partially crushed during use. Also, potting material can surround the elastic conductive material, thus reducing the amount of pressure the elastic conductive material exerts on the contact points.
The Bolan module also has a relatively slow transfer rate of data into and out of the module due to the crude time base of an unstabilized oscillator. Although the crude time base of an unstabilized oscillator can be laser trimmed for higher transfer rates, this process adds cost.